Piston



Sept. 13, 1932; Q BERRY 1,877,490

' PISTON Filed March 20, 1922 2 Sheets-Sheet 1 INVENTOR Sept. 13, 1932.

PISTON Filed March 20, 1922 2 sheets-s eet 2 INVENTOR.

ATTORNEY.

o. c. BERRY 0.

Patented Sept. 13, 1932 f OTTO CARTER BERRY, OF INDIANAPOLTS, INDIANA PISTON Application filed larch 20, 1922 Serial no. 545,312.

It is the object of my invention to produce an internal-combustion-en ine piston which has all the advantages non-ferrous pistons, but which is free from the disadvantages usually incident to non-ferrous pistons, such as excessive expansion upon heating. The clearance between the piston and the cylinder of aninternal combustion engine must be kept within close limits. The exact clearance for best performance will vary somewhat with different engines and difi'erent conditions, but for any specific engine the proper limits are definitely determinable. Failure to keep within these limits will result in inferior engine performance. The temperature of both the piston and the cylinder vary under different operating conditions, and the metal of both expands as the temperature increases. The piston gets hotter than does the cylinder wall, and therefore expands more, thus ordinarily making the clearance less in a hot than in a cold engine. When the co-eflicient of expension is small, however, and is the same in both the piston and the cylinder, this difference in expansion may be kept within the allowable limits of the clearance variation. Thus when both the piston and the cylinder are made of cast iron it is not difficult to avoid at least the greater part of the troubles due to clearance. v There are a number of non-ferrous alloys which in certain respects are superior to cast iron as piston metals. The are lighter, have a lower co-efiicient of frictlon, have a higher thermal conductivity, and are usually softer than cast iron so that in case of trouble the are not so apt to score the cylinder wal These advantages are important, and have certain disadvantages.

The disadvantages of thiese non-ferrous metals are due largely to their higher thermal co-efficient of expansion. The piston that is a proper fit when the engine is at normal operating temperatures will be excessively loose when the engine is cold, and at the same time will be too tight when the temperature rises above normal. If the piston has the proper clearance when the engine led to the use of these metals in spite of is cold, it will become so tight that it will seize when the engine is in operation. I As already stated, the object of the present invention is to make possible the use of non-ferrous metal in a piston and yet to elimmate the disadvantages due to their high coefficients of expansion. In doing this I prefer to introduce a number of refinements, which will appear hereinafter, but which are not essential to the invention in its broader o aspects.

The accompanying drawings illustrate my invention in its preferred form: Fig. 1 is an elevation of a piston embodying my invention, viewed in the line of the wrist pin; 5 Fig. 2 is a bottom plan of the piston shown in Fig. 1; Fig. 3 is a vertical central section, on the line 3-3 of Fig. 2; Fig. 4 is a vertical section on the line 44 of Fig. 2; and Fig.

5 is a fragmental section on the line 5--5 p of Fig. 2.

My improved piston has a head-part10 and a skirt, which latter preferably comprises two opposite skirt-segments 11. The head-part 10 at its periphery isof only sufficient axial length to provide a ring-belt for piston rings 13, to co-operate in the usual way with the inner wall of the cylinder 14, and below such peripheral piston-ring part the head-part 10 is spaced from the skirt segments 1-1 by a' gap 15, so that the sectional skirt is separate from the head-part. The head-part 10 is provided witha depending medial cross-rib 16, in the vertical plane of the wrist pin and directly above it, and the ends of this cross-rib extend downward and are integral with wrist-pin bosses 17, which are also connected to the head-part 10 by. webs 18 transverse to the cross-rib 16 and The wrist-pin bosses 17 are well below the lower edge of the peripheral part of the head-part 10, so that they lie between the two skirt-segments 11; and the'cross-rib 16 and webs 18 make a strong thrust connection be- 95 tween the head-part 10 and the bosses 17.

The skirt-segments 11 are opposite each /other on a piston-diameter perpendicular to the wrist pin, so that they are in a position to take the reaction component from the 109 joining the bosses 17 near their outer ends. i

sometimes oblique connecting rod in a direction perpendicular to the cylinder wall in the plane of the swing of the connecting rod. In other words, these skirt-segments form bearing shoes for the piston against the cylinder wall, or cross-head bearings for the upper end of the connecting rod. These skirt-segments 11 preferably have horizontal strengthening ribs 19- near their upper and lower edges and at one or more inter mediate points on their inside faces, and also have vertically extending thickened portions or ribs 20 near their lateral ed es.

. The head-part 10 and the sklrt-segments 11 are both made of some non-ferrous metal, such as aluminum or an aluminum alloy; whereby they have certain advantages of lightness, high thermal conductivity, and low co-eflicient of friction. The head-part 10 is made of sufliciently small diameter 'so that even though its co-eflicient of expansion is greater than that of the cylinder it never expands sufliciently to bind; but the bearing parts of skirt segments 11 are made to .fit rather closely against the .inner surface of the cylinder 14, and are prevented from bindfrom the non-ferrous metal in which ing by the arrangement by which they are connected together and to the head-part 10.

Such connection is made by corrugated sheet-metal members 21, or struts, whichextend from one skirt-segment 11 to the other and are connected to the wrist-pin bosses 17 intermediately. The corrugated members or struts 21 have their ends embedded in the vertically extending thickened portions 20 of the skirt-segments 11, and a middle portion embedded in circumferential ribs 22 at or near the inner ends of the wrist-pin bosses and bridge spaces which intervene between said bosses and the skirt-segments. The corrugated members or struts 21 have. suitable openings through them at the wrist-pin bosses for the wrist pins to pass through, the holes being sufliciently large so that such corrugated portions do not reach the bearing surfaces of such bosses.

The corrugated members or struts 21 are made of some strong metal having a co-eflicient of expansion not greater than that of the metal of the cylinder 14, and preferably of a metal having a smaller co-efiicient of expansion than has such cylinder metal, so that there will be a sufficient margin to allow for the greater heating of the piston than of the cylinder. The cylinder 14 being almost universall of cast iron, I find that steel .is

perhaps t e most suitable material forfth e corrugated members 20; and I. prefer touse "a steel which hasa .co-efiicient of expansion materiall less than that of cast iron; I prefer to ma e the members 20 of sheet steel, cor;

rugated' for greater strength. i

Also, to avoid the tearing loose of this steel arts ofit are embedded and which has a di erent co-efiicient of'expansion, I prefer to provide the members or struts 21 at their ends which are embedded in the skirt-segments 11 with slits 23 located at the crests of the various corrugations, as is clear from Figs. 1, 3, and i substantially no edgewise bending of the ,i';

sheet metals.

A proper joining of the two metals of the corrugated members or struts to the wristpin bosses and skirt-segments may be obtained in any suitable manner. -An eflicient way of obtaining such joining, and one I prefer, is by first coating at least the parts to be embedded of the corrugated members 21 with zinc, as b the process-known as sherardizing, and t en embedding the zinccoated parts in the non-ferrous alloy while the latter is in molten state. Although there is some difficulty in getting adhesion directly between steel and aluminum or aluminum alloys, which are the preferable non-ferrous alloys for this purpose, the zinc coating overcomes this difficulty by adhering to both the steel and the aluminum alloys, so that a rigid joint is obtained between the corrugated members and the parts in which they are embedded.

In making my piston, I conveniently make the corrugated members or struts 21 as sheetmetal stampin s; sherardize them, or their parts to be em edded; suitably mount them in a mold in whichthe parts 10 and 11 are tosbe cast; and cast such parts 10 and 11 in su h 'mold, preferably simultaneously, to em ed the proper parts of the sheet-metal members 21 in the thickened portions 20 of the skirt-segments and the circumferential ribs 22 of'the wrist-pin bosses. If desired, the skirt-segments may be cast continuous with theperipheral portions of the head-part 10, and subsequently sawed apart to separate them and form the gaps 15. The rough piston thus produced is then finishedlin the usual way of pistons,to provide proper clearances for both the skirt-segments and the head-part. As already stated, this clearance is relatively lar e for the head-part 10, to allow for the di erential expansion ofit and the cylinder, but is relatively small for the skirt section 11, there bein just sufiicient clearance to permit proper lu rication. This small clearance is substantially maintained under all conditions of operation, because as the engine heats and the cylinder 14 expands the segments 11 are prevented from separating from each other sufiiciently rapidly to i 2. A piston, comprising a head-part of non ferrous metal, Wrist-pin bosses rigidly connected to said head-part, skirt segments also of non-ferrous metal, and spaced from said wrist-pin bosses, members made of a metal different from said head-part and skirt-segments and each connectingsaidskirtsegments together and to said wrist-pin bosses and controlling the spacing between said skirt segments.

3. A piston, comprising a head-part, wristpin bosses rigidly connected to said head-part,

skirt segment spaced from said wrist-pin bosses, and members made of a metal having a themal co-efiicient of expansion smaller than that of the metal in said head-part and connecting said skirt segments together and to said wrist-pin bosses.

4. A piston, comprising a head-part made of non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, skirt segments also made of said non-ferrous metal and spaced from said wrist-pin bosses, and members made of aferrous metal and each connecting said skirt segments together and to said wrist-pin bosses and controlling the spacing between said skirt segments.

5. A piston, comprising a head-part of non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, skirt segments, and members made of a metal having a thermal co-elficient of expansion smaller than that of the metal in said head-part, the extreme ends of said members being imbedded in said skirt-segments, and intermediate portions thereof being imbedded in. the wrist-pin bosses, said members connecting said skirtsegments together and to said wrist-pin bosses.

6. A piston, comprising a head-partof non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, skirt segments spaced from said wrist-pin bosses, and members made of sheet metal connecting said skirt segments together and .to said wristpin bosses.

7. A piston, comprising a head part, wrist pin bosses rigidly connected to said headpart, skirt segments, and members made of corrugated sheet metal connecting said skirtsegments together and to said wrist-pin bosses.

V 8; A piston, comprlsing a headpart with depending wrist-pin bosses, skirt segments, and members made of corrugated sheet metal, the ends of said members being slotted at the crests of the corrugations, said members connectin said skirt-segments together and to said wrist-pin bosses.

9. A piston, comprising a head-part of non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, skirt segments, and members made of a corrugated sheet metal of a ferrous composition; the extreme ends of said members being cast into the skirt-segments, ing cast into the wrist-pin bosses, said mem bers connecting said skirt segmentstogether and to said wrist-pin bosses.

p 10. A piston, comprising a head-part, wrist-pin bosses connected to said head-part, skirt segments, and members made of corrugated sheet metal, the extreme ends of said members being slotted and cast into said and intermediate portions beskirt-se ments and an intermediate portion segments and intermediate portions thereofbein cast into said wrist-pin bosses, said vmemiers connecting said skirt segments together and to said wrist-pin bosses.

12. A piston, comprising a head-part and wrist-pin bosses, skirt segments spaced from the aforesaid parts, and connecting plates of different metal from and having a cast-in joint with the skirt segments and connecting said skirt segments to the remainder of the piston.

13. A piston, comprising a head-part and wrist-pin bosses, skirt segments spaced from the aforesaid parts, said head-part and skirt segments being of non-ferrous metal, and connecting plates of ferrous metal connecting said skirt segments to the remainder of the piston and having cast-in parts which they connect.

14. In a piston, a sectional skirt, a head separate therefrom, and struts uniting the sections of the skirt to each other and to the head, said struts having openings for the piston pin and having their edges adj acentthe piston pin bearings buried in the material of said bearings, substantially as ,set 'forth. 15. In a piston, ahead, a separate sectional skirt of aluminum allo and steel struts extending transversely o the piston pin bearings uniting the sections to each other and to the head, said struts having their opposite ends buriedin the respective skirt sections, substantially as set forth.

16. In a piston, a head, piston pin bosses injoints with the opposed arcuate aprons supported by the end portions of said struts, substantially as set forth.

17. In a piston, a head with integral piston pin bosses, a sectional skirt independent of said head, and struts extending from the skirt aprons part way into the piston pin bosses uniting the head to the skirt, substantially as set forth.

18. In a piston, a sectional skirt, a head separate from the sections of the skirt, said head and skirt consisting of expansible material, and struts of relatively inexpansible material uniting said sections of the skirt to the head and to each other, said struts extending transversely of the piston pin bearings and having their edges adjacent said piston in bearings buried in the material of said earings', substantially as set forth.

19. In a piston, a head, a separate skirt of material having a high cocflicient of expansion, and transverse struts of less expansible material arranged as chords' of circles inter secting the cylinder, said struts connecting opposite sides of the skirt, substantially as set forth.

20. In a piston, a head, a separate skirt of material having a high coefficient of expansion, and transverse struts of less expansible material arranged to limit expansion of the skirt in a direction transverse to the piston pin, substantially as set forth.

21. In a piston, the combination of a head and a skirt having thrust faces made of a material having'a relatively high coefficient of expansion, said thrust faces being separated from the head, and connectors of a material having a lower coefiicient of expansion than the material of the skirt completely anchored at either end in one of said thrust faces and extending across the piston.

22. In combination, a piston head having wrist pin bosses integral therewith, a piston skirt having cut out portions around the outside faces of said bosses, struts secured to said skirt and across said bosses, to control the expansion and contraction of said skirt, said struts having a lower coeflicient of expansion than cast iron.

23. In a piston, the combination of a head and skirt portion of a material having a relatively vhigh co-eflicient of expansion, piston pin bosses in said skirt portion, and means made of a material of a lesser co-efiicient of expansion, extending along and connected with said skirt portion over a considerable range beginning above and extending to below and including the regions occupied by the bosses and limiting the rate of expansion of said skirt throughout said range, said pis ton being slitted to separate the thrust faces of the skirt from the head and being relieved in the regions of the piston pin bosses.

24. In a piston,'the combination of a head having ring grooves therein and skirt portion of aluminum alloy, piston pin bosses ins-aid skirt portion, and means of ferrous metal extending along and connected with said skirt portion over a considerable range, beginning below the ring grooves and above the bosses and extending to below and including the regions occupied by the bosses, and limiting the diametrical expansion of said skirt throughout said range, said piston being slitted to separate the thrust faces of the skirt from the head and being cut away in the regions of the piston pin bosses.

25. In a piston, a sectional skirt, a head eparate from the sections of the skirt, piston pin bearings integral with the head, said head and skirt consisting of expa-nsible material, and struts of relatively inexpansible material uniting said sections of the skirt to the head and to each other, the struts having openings coaxial with the piston pin bearings and the material of said bearings enveloping parts of said struts, substantially as set forth.

26. In a piston, a head, piston pin bearing bosses integral with the head, two struts of relatively inexpansible material each having an intermediate portion enveloped by the neck of a piston pin bearing boss, and a skirt with opposed arcuate aprons supported by the end portions of said struts, the skirt comprising a plurality of separate sections, substantially as set forth.

27. In apiston, independent component parts of cast metal, and a common system of metallic struts to which said independent cast-metal parts are secured by cast-in joints.

28. In a piston, independent component parts of cast metal, including a head portion and a plurality of separate skirt portions, and a common system of metallic struts to which said independent cast-metal parts are secured by cast-in joints.

29. In a piston, a skirt with separate op posed arcuate aprons, and struts of differentmaterial having their opposite ends buried in the material of said aprons, substantially as set forth. u

30. In a piston, a head having piston pin bosses integral therewith, a skirt having separate sections, and struts having openings for the piston pins, said struts having their ends buried in the material of the skirt sections and their margins adjacent the bosses buried in said bosses, substantially as set forth.

31. In a piston, a sectional skirt of material havlng a large coeificient of expansion, a head separate therefrom, piston pin bear- 1ngs on the head, rigid struts of material having a smaller coeflicient of expansion unitmg the sections of the skirt to each other and to the head above and below said bearings,

- skirt of of chordal struts, ing between the and means for securing said parts together, substantially as set forth.

32. In a piston, separate arctuate aprons adapted to expand circumferentially of the piston, and relatively-inexpansible transverse struts connecting opposed aprons to limit radial expansion or contraction, substantially as set forth.

33. In a piston, a head, a separate sectional material having a high coeflicient of expansion, and transverse struts of less expansible material arranged as chords of circles intersecting the cylinder, said struts connecting adjacent edges of oppositely located sections of the skirt, substantially as set forth.

34:. In a piston, a head having pin bosses formed thereon, a skirt having wall-bearing portions, and relatively inexpansible struts embedded in said pin bosses, the ends of said struts being attached to said wall bearing portions, substantially as set forth.

35. A piston having a head, piers depending from the head, piston pin bearings formed in the piers, cylinder-bearing portions on opposite sides of the piston, a pair each of said struts extendthe intermediate portion of each strut being surrounded by the material of a pier, there being an integral connection between each of the cylinder-bearing portions and each pier.

36. A' wrist-pin part, skirt segments spaced from said wristin boss, and a member made of a metal diferent from said skirt segments and connecting said skirt segments together and to said wrist-pin boss and controlling the spacing between said skirt segments.

.37. A non-ferrous metal, a wrlst-pin bossrigidly iston, comprising a head-part, a

cylinder-bearing portions,

said skirt segments to the remainder of the piston and having cast-in joints with the parts which it connects.

40. A piston, comprising a head-part of non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, sk' and substantially chordal members made 0 a metal having a thermal co-eflicient of expansion smaller than that of the metal in said head-part and joined to said skirt segments and separately joined to said wristpin bosses.

41. A piston, comprising a head-part of non-ferrous metal, wrist-pin bosses rigidly connected to said head-part, skirt segments between which and sad wrist-pin bosses spaces intervene, and substantially chordal members made of a metal having a thermal co-eflicient of expansion smallerthan that of the metal in said head-part and bridging said spaces and joined to said skirt segments and separately joined to said wrist-pin bosses. witness whereof, I have hereunto set my hand at Indianapolis, Indiana, this 17th day of March, A. D. one thousand nine hundredcand twenty-two.

' OTTO CARTER BERRY.

oss rigidly connected to said headpiston, comprising a head-part of,

connected to said head-part, skirt segments r also made of non-ferrous from said wrist-pin boss, and a. member made of a metal different from said headart and skirt-segments and connecting said s irt segments together and to said wrist-pin boss and controlling the spacing between said skirt segments.

38. A piston, of non-ferrous idly connected comprising a head-part made metal, a wrist-pin boss rigto said head-part, skirt seg j ments also made of said non-ferrous metal and spaced from said wrist-pin'boss, and a. member made of a ferrous metal and connecting said skirt segments together and to said wrist-pin boss and controlling the spacf ing between said skirt segmn 39. A piston, comprising a head-partand a wrist-pin boss, skirt segments spaced from the aforesaid parts, said head-part andskirt segments being of non-ferrous metal, and a connecting plate of ferrous metal connecting metal and spaced lrt segments 

